Neuroticism, defined as a dispositional tendency to experience negative emotions, is often elevated in individuals with depression. This personality trait is typically assessed through self-report measures and has been shown to increase during depressive episodes. Importantly, neuroticism is also moderately heritable. Twin studies further suggest that neuroticism and depression share common genetic influences, indicating overlapping biological foundations between the trait and the disorder.

Neuroticism as an Endophenotype

Cortisol, a marker of HPA axis functioning, has been widely studied in depression due to its links with stress and role in the development of the disorder. Depressed individuals often show elevated morning cortisol and an increased cortisol awakening response (CAR), although findings are somewhat inconsistent. CAR has stronger evidence of state-independence, as elevations are observed even in remission. Additionally, elevated cortisol levels have been found in healthy offspring of depressed parents and may predict the onset of symptoms. Overall, there is moderate support for CAR and morning cortisol as an endophenotype for depression.

Cortisol (CAR) as an endophenotype of depression

Asymmetry in electrical activity in frontal regions is measured via EEG. Generally, activity in the right frontal region is thought to reflect withdrawal behavior and negative affect. The left frontal region reflects approach behavior and positive affect. Depression has been associated with decreased relative left FA. These symptoms have been studied, and it has been found that this trait is only modestly heritable. However, this particular endophenotype is still being researched continually to discover its exact relation to depression.

Frontal Asymmetry

There is new research on deficits in reward processing as a possible endophenotype for depression. A probabilistic reward learning task (PRT) has the most relevant data. Using signal-detection procedures, participants are shown one of two stimuli and instructed to hit a corresponding key. The two stimuli represent different values (one with more value than the other to produce a response bias). Compared with control groups, depressed individuals tend to fail to create a response bias, therefore valuing both stimuli as the same. There is also preliminary evidence that response bias on the PRT shares genes with depression.

Reward Learning

These endophenotypes are less studied and have a more limited evidence base. Both attention and memory have a prominent role in cognitive models of the etiology of depression. These endophenotypes also have important links to depression-related neural dysfunctions.

Cognitive Endophenotypes

Endophenotypes describe the testable components or symptomology related to an overarching phenotype (in this case, depression). There are a large number of endophenotypes related to depression, a few are:

- Cortisol (CAR)
- Frontal asymmetry
- Reward learning (Anhedonia)
- Cognitive biases (attentional and behavioral)
- Neuroticism

Appalachian State University

Generally speaking, depression is an overall feeling of sadness. More specifically, those with depression tend to experience several things such as: an increase or decrease in weight, troubles with concentration, feelings of meaninglessness or worthlessness, thoughts of death or suicide, and so on. 

Depression

Gottesman, I. I., & Gould, T. D. (2003). The endophenotype concept in psychiatry: etymology and strategic intentions. The American journal of psychiatry, 160(4), 636–645. https://doi.org/10.1176/appi.ajp.160.4.636

Cerebral Palsy is known to make the stresses of life more overwhelming. Individuals tend to become shy in social situations out of fear of being bullied or teased by others. They are more prone to depression and anxiety disorders.

Psychological Impacts of Cerebral Palsy

There is not one single factual answer for what causes depression as it is different for everyone but these are some of the most common.  

- abuse
- age
- particular medications
- conflict
- death or loss
- genes
- life changing events
- Illness
- substance misuse

External Causes of Depression 

It has been known that culture affects perception of depression. With this in mind, it is also possible that certain ideological views may have more common rates of mental health problems. There has already been multiple studies into this idea, and it seems that there is a small correlation.

Ideology and Depression

50-70% of all primary care visits are for mental health care; specifically, for treating anxiety, depression, and stress. According to WHO, depression is the leading cause of disability after cardiovascular disease.


Scope of Depression

- Beck Depression Inventory (BDI)
- Center of Epidemiologic studies-Depression Scale (CES-D)
- Hamilton Depression Rating Scale (HAM-D)
- Geriatric Depression Scale (GDS)
- Hospital Anxiety and Depression Scale (HADS)
- Patient Health Questionnaire-9 (PHQ-9)
- Self-report inventory to diagnose depression (IDD)
- Depression, Anxiety, and Stress Scale-21 (DASS-21)


Measures of Depression

emotional symptoms
- hopelessness 
- anxiety

physical systems
- reduced appetite 
- headaches.

Common Symptoms of Depression

References for Depression in South-Asian women

Depression in a common issue in the South-Asian community. Yet it is never talked about due to cultural themes. 

Depression in South-Asian Women

Reference for Major Depression Disorder

Dysfunctional attitudes are unrealistic and maladaptive outlooks that can cause depression by producing self-destructive and pessimistic thoughts about the future and the world.

Dysfunctional Attitudes

Reference for Dysfunctional Attitudes

Reference for Emotion Regulation in Major Depression Disorder

The use of emotion regulation strategies can alter a variety of emotional aspects such as the duration, stability, frequency, or intensity of an emotion. The success of emotion regulation depends on picking the right emotion regulation strategy and the efficient application of the chosen emotion regulation strategy. Some emotion regulation strategies are adaptive while others are maladaptive. Patients with major depression disorder tend to employ less adaptive emotional regulation strategies and more maladaptive emotional regulation strategies which worsens their symptoms.

Emotion Regulation and Major Depression Disorder

Reference for Dysphoria

Dysphoria is an abnormally augmented sad mood.

Dysphoria

Long-term or chronic stress can lead down the path towards depression, affecting appetite, sleep habits, and concentration ability. David Prescott, Ph.D., an associate professor of Health Administration and Public Health at Husson University, states that stress and depression have a casual relationship known to be "bidirectional." Prescott also helps clarify by stating that they can both cause each other. Therefore, stress can cause depression, while also depression can cause stress.

Connection Between Stress and Depression

Reference for Behavioral Activation

Behavioral activation is a form of behavioral therapy that therapists use to help depression patients identify activities related with positive moods. 

Behavioral Activation

Cognitive theories propose that depression is initiated by negative thoughts, interpretations, self-assessments, and expectations. These frameworks are considered diathesis-stress models, suggesting that depression arises from an interaction between a 'cognitive vulnerability'—a predisposition to negative and maladaptive thinking—and the occurrence of stressful life events.

Cognitive Theories of Depression

A 20-year-old individual, who was previously active and social, has been experiencing significant changes over the last two months. They have withdrawn from friends, stopped participating in a sport they once loved, and report feeling exhausted regardless of how much they sleep. They also describe a persistent feeling of emptiness and have difficulty concentrating on their studies, causing their grades to drop. Which of the following statements best analyzes this individual's situation?

This condition is characterized by frequent instances of fatigue during the day, despite receiving an adequate amount of sleep. It is caused by many disorders, one of the most notable being depression.

Excessive daytime sleepiness (hypersomnia)

Women are twice as likely to have major depression than men, although depressive symptoms vary between the two genders. 

Gender Differences

Findings suggest that girls' proclivity for rumination may lead to a lack of emotional awareness, which can lead to a self-perpetuating cycle in which an individual falls deeper into depression.

Self-Perpetuating Cycle

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References for Depression

Include any and all thoughts of self-harm and or thoughts of ending one's life. Can be caused by psychiatric disorders and chronic illness.

Suicidal Ideations

Studies have found that disempowering parenting in Asian American families have led to increased rates of mental distress and depression in Asian American youth. 

Depression in Asian American Families

College students are one of the top age groups at risk for depression due to factors such as academics, social life, and family. 

Depression in College Students

Studies have found that depression is positively correlated with substance abuse, future alcohol use, and an early development of AUD. 

Depression and Substance Abuse

Studies have shown that athletic injuries and mental health are interrelated issues that can negatively affect an athlete's quality of life. For example, an athletic injury can lead to a decline in mental health, while a decline in mental health can lead to a higher risk of athletic injury.

Depression in Athletes

References for Endophenotypes of Depression

Endophenotypes of Depression

According to 18 studies, there is a strong positive correlation between parental divorce and depression in children. In addition, across 54 studies, researchers discovered a pooled OR of 1.29 when studying the association between depression and parental divorce. Therefore, the factor of parental divorce affects the factor of the risk of developing depression in offspring.

Association with Parental Divorce

Reference for Biomarkers of Depression

- higher cortisol

-hypo-hippocampal volume

-hypofrontality

-elevated levels of glutamate in the frontal cortex

-reduced BDNF

-increased inflammation

-increased levels of bacterial markers (LPS)

Biomarkers of Depression

Depression coupled with anxiety was found to have the most detrimental effect on memory ability in veteran soldiers as opposed to sole depressive or anxiety symptoms.

Effects of Depression and Anxiety on Memory

While perfectionism can lead to high achievements in some individuals, maladaptive perfectionism can result in an increased risk of developing depression. This is due to the fact that maladaptive perfectionism is often characterized by low self-esteem, rumination, and an immense pressure to succeed. 

Association with Maladaptive Perfectionism

A study conducted on a group of rural patients with chronic disease found that 53% of the patients tested positive for depression. Of the 53%, more than half of these individuals were unable to afford their medication within the past year. These findings suggest that depression is positively correlated with the inability to pay for medication. 

Association with Inability to Afford Medication

A study found that participants who were exposed to daylight for 1 or more hours during the winter were less at risk of developing depression and or experiencing depressive symptoms. Thus, weather seems to play an important role in a person's likelihood of developing depression. 

Association with Weather and Daylight

A study surveying a group of young adults found that increased social media usage was associated with an increased risk of developing depression. In fact, individuals with the highest self-reported social media time scored higher on a depression scale report compared to other participants. 

Association with Social Media Usage

Researchers found that individuals with a low PIR, Poverty to Income Ratio, are more likely to develop depression. In addition, researchers found that participants with low income scored much higher on the PHQ than their higher income counterparts.

Association with Income

A study found that 63% of adults with PGS, or an intense, persistent feeling of grief, experienced comorbidity with depression.

Association with Prolonged Grief Disorder

Researchers conducted a study with a control group of 19 women, as well as an experimental group of 19 women diagnosed with MDD. Using fMRI, the researchers found that romantic rejection led to heightened neural activity only in the participants diagnosed with MDD. In addition, researchers found that the individuals with MDD experienced more powerful emotions when faced with rejection or acceptance compared to individuals in the control group.

Association between Depressive Symptoms and Romantic Rejection

Longitudinal and cross-longitudinal studies suggest that sleeping later at night is correlated with worse mental health. 

Association with Sleep

Researchers found that 55 to 65 year old adults in the U.S. are susceptible of developing depression if they have subjective expectations of being fired or laid off. 

Association with Subjective Expectations in the Job Market

Studies conducted on a variety of nation's citizens after the events of a war found a rise in many mental disorders, including depression. The most vulnerable groups included women, children, elderly, and those with disabilities. Researchers also noted the increased usage of culture and religion as coping strategies in these areas.

Association with War

In a study conducted on 2,267 workers with depression, researchers found that a single leave of absence was attributed to a mild depressive episode, while multiple leave of absences were attributed to recurrent MDD. Thus, the more severe or frequent the depressive episode, the more likely an employee was to take a leave of absence.  

Association with Leave of Absence

After studying a number of high school dropouts and at risk individuals at 12 underserved schools in Canada, researchers found that 1 out of 4 dropouts had experienced severe clinical depression in the three months before their departure. In addition, students who had experienced recent depressive symptoms were more than twice as likely to drop out compared to other students. 

Association with High School Dropout Rates

Research has proven that a history of being bullied and or a history of bullying others can make an individual more susceptible to developing depression. A research review of 31 studies revealed that children and teenagers who were bullied were 2.77 times likely of developing depression, while children and teenagers who bullied others were 1.73 times more likely of developing depression.

Association with Bullying

Using the PHQ-9 to measure depressive symptoms and data from the Seoul Government Survey on Socially Isolated and Withdrawn Young Adults, researchers deduced that the more depressed young adults were, the more likely they were to be in social isolation. In addition, prolonged isolation (isolation over three years) was also positively associated with depression. 

Association with Social Isolation

An online survey conducted on 1,913 undergraduate students in Bangladesh revealed that students vulnerable to depression were 65% less likely to maintain healthy hygiene practices. The survey was also able to differentiate hygiene practices by gender, as the results showed 90.1% of females possessed good hygiene compared to 75% of their male counterparts. In addition, the survey showed that those who lived in better accommodations were more likely to practice better hygiene and less likely to develop depression.

Association with Personal Hygiene

Recent research supports the idea that individuals who possess certain personality traits are more at risk of developing depression. In particular, researchers noted that if present, the traits neuroticism and or negative emotionality were able to predict the development of specific depressive disorders. 

Association with Personality Traits

Researchers discovered that 40 out of 60 patients with agoraphobia or panic disorder had experienced or were experiencing a major depressive episode. In addition, patients with previous MDD episodes were more likely to have severe anxiety.

Association with Agoraphobia 

Fatigue is a common residual symptom in depressive patients due to the lack of complete effectiveness of antidepressant medications. Many providers address this by decreasing patients' antidepressant dosages or by switching medications. 

Association with Fatigue

Research demonstrates a negative correlation between spirituality and depression. Patients who score higher on measures of spiritual involvement—such as belief in a higher authority, prioritizing prayer, and finding gratitude and purpose amid obstacles—are less likely to be depressed or tend to experience less severe depressive symptoms.

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